The S-alkanyl thiolcarbamate compounds are used in industry as plastic (synthetic) materials for the preparation of polymeric substances and as intermediates for the production of plant protecting agents; while the S-alkylthiolcarbamate compounds of the latter type are employed as active ingredients of plant protecting compositions in the agriculture.
A widely used method for preparing vinyl compounds comprises the addition of a substance containing a mobile hydrogen to acetylene. The possibilities of utilizing this method have been described by W. Reppe [Ann. 601, 81-138 (1956)] reporting on the preparation of a number of vinyl compounds; however, alkenyl esters of thiolcarbamic acids have not been disclosed.
C. G. Overberger et al. [J. Org. Chem. 27, 4331-4337 (1962)] were the first to work out a method for preparing S-(1-alkenyl)esters of monothiocarbamic acids. The principle of their method comprises the splitting off by potassium tertiary-butoxide from an S-(.beta.-chloroethyl)monothiocarbamate prepared previously. This process, still giving good yields, did not become widely utilized in the practice because the starting materials are expensive, corrosive and toxic in character.
Practically, S-alkyl thiolcarbamates of the formula (I) are obtained by reacting a primary, secondary or tertiary ammonium salt or an alkaline metal salt of the appropriate thilcarbamic acid with an alkyl halide (Soviet patent specifications Nos. 224,511 and 186,437; DT-PS Nos. 2,513,196 and 2,844,305; Japan patent specifications Nos. 75 76026, 78 25564, 77 28832 and 77 746027; as well as U.S. Pat. Nos. 3,167,571 and 3,151,119).
According to the DT-PS Nos. 2,212,766 and 2,117,115 as well as to U.S. Pat. No. 4,066,081, phosgene is brought into reaction with alkyl mercaptans and the alkyl chlorothioformates obtained are reacted with primary or secondary amines.
S-Alkyl thiolcarbamates can also be prepared by reacting carbamoyl chloride with alkyl mercaptans (U.S. Pat. Nos. 2,983,747 and 2,913,327; as well as Spanish patent specification No. 422,149).
According to DT-PS No. 2,703,106, thiolcarbamates are obtained by treating dithiocarbamates with dimethyl sulphate and elementary iodine.
According to DT-PS No. 2,461,876 O-alkyl thiocarbamates are heated with dialkyl sulphates to give S-alkyl esters via isomerization.
According to U.S. Pat. No. 4,071,423, thiolcarbamates are obtained in an extraordinarily high yield by the radical addition of thiolcarbamate salts to olefins.
All these processes require expensive starting materials or create a severe burden upon health and environment.